The invention relates generally to a power management control system and in particular, to a power management control system in which a plurality of power monitoring and control devices are coupled to a computer through a common bus.
In today's power management control systems, a variety of power monitoring or control devices are connected to a common bus which allows the power monitoring or control devices to communicate with a server. One standard protocol used for communicating between the server and the power control and monitoring devices is the Modbus RTU standard. There are many Modbus RTU/DDE Servers commercially available for a wide variety of applications. All major electrical distribution companies have a similar product. The narrow scope of these servers are their major limitation. These systems expect the client applications (Man-Machine Interfaces) to handle the complexities of the actual power controlling and metering devices. Many of the servers are designed to communicate using a protocol designed for use with only certain devices, family of devices or specially designed devices. Also, not all the servers are able to support any generic Modbus RTU compliant device.
FIG. 1 (herein labeled prior art) is a network diagram of General Electric Co.'s power leader distribution system shown at 98. System 98 comprises a computer 100 having a Commnet network interface card 102 installed in one of its I/O slots. The computer contains software for monitoring and controlling selected aspects power usage/consumption. Card 102 provides a Commnet I/O port which defines a Commnet bus 104. As is known, trip units 106, e.g., Trip, Enhanced Trip-D, Trip PM and Enhanced Trip-C Units, which are commercially available from General Electric Co., are connected for communication over bus 104. Meters 108, e.g., Power Leader Meters commercially available from General Electric Co., are connected for communication over bus 104. Relays 110, e.g., Spectra ECM and General Electric Co.'s Power Leader MDP, are connected for communication over bus 104. Control devices 112, e.g., Multilin models 269 and 565, are connected through product interface modules 114 for communication over bus 104. The product interface modules 114 are required, as these control devices are not directly compatible with the Commnet bus. Communication rates on the Commnet bus are relatively slow by today's standards. Further, the Commnet bus is a protocol of General Electric Co. and not an industry standard. Accordingly, many commercially available devices, in particular non General Electric Co. devices, are not compatible with the Comment bus. There is a need to standardize bus protocol in this industry, whereby a customer will be able to configure and/or purchase replace devices or upgrades from a number of manufactures.
Another power monitoring system is described in U.S. Pat. No. 5,381,462 entitled "Utility Monitor Communications Systems." The system includes a meter reading terminal which gathers data from utility meters and sends that data to a utility company's host computer via phone lines. The system uses a variety of error-detection procedures and communications protocols to ensure a high degree of reliability in communicating data to and from the central office and the meter reading terminal. The system also allows immediate interruption of communications should the customer attempt to use the telephone line.